CN113136529B - Medium manganese drill rod and preparation method thereof - Google Patents
Medium manganese drill rod and preparation method thereof Download PDFInfo
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- CN113136529B CN113136529B CN202110262211.2A CN202110262211A CN113136529B CN 113136529 B CN113136529 B CN 113136529B CN 202110262211 A CN202110262211 A CN 202110262211A CN 113136529 B CN113136529 B CN 113136529B
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- 239000011572 manganese Substances 0.000 title claims abstract description 52
- 229910052748 manganese Inorganic materials 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 title claims description 27
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 75
- 239000010959 steel Substances 0.000 claims abstract description 75
- 238000010438 heat treatment Methods 0.000 claims abstract description 55
- 229910000617 Mangalloy Inorganic materials 0.000 claims abstract description 40
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 36
- 238000000034 method Methods 0.000 claims abstract description 28
- 239000000126 substance Substances 0.000 claims abstract description 20
- 239000012535 impurity Substances 0.000 claims abstract description 19
- 238000001816 cooling Methods 0.000 claims description 41
- 239000011162 core material Substances 0.000 claims description 34
- 229910001566 austenite Inorganic materials 0.000 claims description 29
- 238000005553 drilling Methods 0.000 claims description 22
- 229910000734 martensite Inorganic materials 0.000 claims description 22
- 238000007670 refining Methods 0.000 claims description 17
- 238000005098 hot rolling Methods 0.000 claims description 12
- 238000003723 Smelting Methods 0.000 claims description 11
- 238000004513 sizing Methods 0.000 claims description 11
- 239000002994 raw material Substances 0.000 claims description 10
- 238000004321 preservation Methods 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 18
- 230000000052 comparative effect Effects 0.000 description 13
- 230000000694 effects Effects 0.000 description 12
- 230000000717 retained effect Effects 0.000 description 12
- 230000002411 adverse Effects 0.000 description 9
- 230000001276 controlling effect Effects 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 238000009749 continuous casting Methods 0.000 description 7
- 238000010583 slow cooling Methods 0.000 description 7
- 230000035939 shock Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 3
- 239000011435 rock Substances 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 238000005204 segregation Methods 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910003296 Ni-Mo Inorganic materials 0.000 description 1
- 229910008458 Si—Cr Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 239000000368 lamellar mixture Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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- Chemical & Material Sciences (AREA)
- Geology (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
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Abstract
The invention particularly relates to low-carbon medium-manganese steel, a medium-manganese drill rod and a preparation method thereof, belonging to the technical field of steel preparation, wherein the steel comprises the following chemical components in percentage by mass: c: 0.05% -0.25%, Si: 0.20% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010%, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities; compared with the traditional drill rod, the tensile strength is more than 1250Mpa, the yield strength is more than 900Mpa, the elongation is more than 20%, the product of strength and elongation is 25-35 GPa%, the toughness is good, the requirement of the drill rod can be met, the service life is long, the existing drill rod heat treatment tool equipment can be utilized, and the heat treatment process is simple and feasible.
Description
Technical Field
The invention belongs to the technical field of steel preparation, and particularly relates to low-carbon medium-manganese steel, a medium-manganese drill rod and a preparation method thereof.
Background
Rock drilling tools are widely used in mining fields such as mines and coal mines, and the whole drilling tool system comprises four major types: the drill rod, the drill bit, the connecting sleeve and the drill bit shank. The drill rod is used as a stress piece in rock drilling and drilling, and the steel is required to have the characteristics of high strength, wear resistance, good fatigue property, impact resistance and the like. In general, drill rods are manufactured by heat treatment of steel, such as bulk carburization, normalization, etc., or by directly rolling steel.
The applicant finds in the course of the invention: the drill rod manufactured by rolling has poor fatigue resistance and insufficient shock resistance, and the toughness of steel is improved and the elongation and the shock resistance are improved by adopting a heat treatment method such as medium-frequency induction heating incomplete normalizing, but the incomplete normalizing process is unstable and the shock resistance and the toughness of the drill rod are still insufficient.
The steel for heavy drill rods at home and abroad adopts a Cr-Ni-Mo system, and is used after integral carburization, so that the alloy cost is high, and the heat treatment period is long. For example: the patent application CN104928590A discloses Mn-Si-Cr low-carbon bainite steel, a drill rod and preparation thereof, which optimizes the components and process of the existing heavy-duty drill steel, but the applicant finds that the product of strength and elongation of the bainite structure is still not high, and the product of strength and elongation of the drill rod obtained according to the disclosed example is 19.2-22.4 Gpa. The steel for the taper drill rod is 95CrMo, the structure form of the steel is high-carbon lamellar pearlite, the pearlite structure is a mechanical lamellar mixture of ferrite and cementite, and the performance of the steel limits further improvement of elongation and product of strength and elongation from the structure phase composition; the patent application No. CN 109252030A discloses a control method for improving the plasticity of 95CrMo hollow steel, which obtains the performance of hollow steel with good plasticity by innovating a production process, but the applicant finds that the product of strength and plasticity is not more than 20 Gpa.
Disclosure of Invention
In view of the above, the present invention has been made in order to provide a low carbon medium manganese steel and a medium manganese drill rod and a method of making which overcome the above problems or at least partially solve the above problems.
The embodiment of the invention provides low-carbon medium manganese steel, which comprises the following chemical components in percentage by mass:
c: 0.05% -0.25%, Si: 0.20% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010%, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
Optionally, the steel comprises the following chemical components in percentage by mass:
c: 0.05% -0.10%, Si: 0.20% -1.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
Optionally, the steel comprises the following chemical components in percentage by mass:
c: 0.10% -0.25%, Si: 1.0% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
Optionally, the H content of the steel is less than 1.5ppm and the O content of the steel is less than 10ppm in mass fraction.
Optionally, the microstructure of the steel is, in volume fraction: 85-94% of lath martensite, 5-10% of retained austenite and 1-5% of carbide.
Optionally, the lath martensite has a width of 0.2-0.6 μm, the equivalent grain size of the retained austenite is 120-460nm, and the carbide size is 20-100 nm.
Based on the same inventive concept, the embodiment of the invention also provides a medium manganese drill rod, and the medium manganese drill rod is prepared from the low-carbon medium manganese steel.
Based on the same inventive concept, the embodiment of the invention also provides a preparation method of the medium manganese drill rod, which comprises the following steps:
obtaining a billet of the low-carbon medium-manganese steel;
carrying out center drilling and core material loading on the steel billet; obtaining square steel of low-carbon medium manganese steel;
heating the square steel for the first time, and then carrying out hot rolling, sizing, cooling and core pulling to obtain a drill rod primary product; the temperature of the first heating is controlled to be 1150-1250 ℃;
carrying out secondary heating, heat preservation and controlled cooling treatment on the primary drill rod product to obtain a medium manganese drill rod; the temperature of the second heating is 800-950 ℃, and the heat preservation time is 2-48 h.
Optionally, the preparation method of the steel billet comprises the following steps:
obtaining raw materials, wherein the raw materials are prepared according to a ratio;
and smelting the raw materials, refining in an LF furnace, performing VD vacuum and continuously casting to obtain the billet.
Optionally, the controlled cooling treatment includes:
cooling the primary drill rod product to 10-200 ℃ at the cooling rate of 20-35 ℃, then heating to 600-900 ℃, preserving heat for 10-480 min, and then cooling to room temperature.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
the embodiment of the invention provides low-carbon medium manganese steel, which comprises the following chemical components in percentage by mass: c: 0.05% -0.25%, Si: 0.20% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities; compared with the traditional drill rod, the tensile strength is more than 1250Mpa, the yield strength is more than 900Mpa, the elongation is more than 20%, the product of strength and elongation is 25-35 GPa%, the toughness is good, the requirement of the drill rod can be met, the service life is long, the existing drill rod heat treatment tool equipment can be utilized, and the heat treatment process is simple and feasible.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a flow chart of a method of making a drill rod according to an embodiment of the present invention;
FIG. 2 is a scanning electron microscope image of the drill rod microstructure provided in example 2 of the present invention;
FIG. 3 is a scanning electron micrograph of the microstructure of a drill rod provided in example 3 of the present invention.
Detailed Description
The present invention will be specifically explained below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented thereby. It will be understood by those skilled in the art that these specific embodiments and examples are illustrative of the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically indicated, various raw materials, reagents, instruments, equipment and the like used in the present invention may be commercially available or may be prepared by existing methods.
At present, the drill rod has two manufacturing modes, one mode is that steel is manufactured after heat treatment, such as integral carburization, normalizing and the like, and the other mode is that the steel is directly rolled to manufacture the drill rod; the applicant finds in the course of the invention that: the drill rod manufactured by rolling has poor fatigue resistance and insufficient shock resistance, and the toughness of steel is improved by adopting a heat treatment method such as medium-frequency induction heating incomplete normalizing, so that the elongation and the shock resistance are improved, but the incomplete normalizing process is unstable, and the shock resistance and the toughness of the drill rod are still insufficient; the applicant creatively finds that the medium manganese steel (the manganese mass fraction is 3% -9%) obtains a ferrite phase (annealed lath martensite) and a residual austenite structure through austenite reversion, the tensile strength of the medium manganese steel is 1.0-1.5Gpa, the elongation is 20% -30%, and the product of strength and elongation reaches more than 30 Gpa.
According to a typical embodiment of the invention, the low-carbon medium-manganese steel comprises the following chemical components in percentage by mass: c: 0.05% -0.25%, Si: 0.20% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
C is an austenite stabilizing element, the reason for controlling the mass fraction of C to be 0.05-0.25% is to obtain proper strength and phase proportion, the adverse effect of overlarge mass fraction value is welding performance, brittleness is increased, material performance is deteriorated, and the disadvantage of undersize is strength improvement;
si is a solid solution strengthening element, the reason for controlling the mass fraction of Si to be 0.20-2.0% is to inhibit carbide precipitation and improve the stability of austenite, the excessive value of the mass fraction is not beneficial to controlling the surface quality of steel, and the excessive value is not beneficial to improving the strength;
mn is a main alloy element of the medium manganese steel, has the functions of expanding an austenite phase region and improving austenite stability control, and the reason that the mass fraction of Mn is 5.0-9.0% is that a full lath martensite structure is obtained at normal temperature and the proportion relation of the structure is adjusted during annealing;
p is a residual element, and the reason for controlling the mass fraction of P to be less than or equal to 0.010 percent is to avoid the disadvantage of excessive P segregation in grain boundaries to the brittleness of steel.
S is a residual element, and the reason for controlling the mass fraction of S to be less than or equal to 0.001 percent is to avoid the disadvantage of the excessive S segregation at grain boundaries and the formation of sulfides on the brittleness of steel.
The low-carbon medium manganese steel provided by the embodiment of the application takes Mn as a main alloy element, does not need to add elements such as Ni and Mo, is low in alloy cost, is particularly suitable for preparing a drill rod, and compared with the traditional drill rod, the tensile strength is greater than 1250Mpa, the yield strength is greater than 900Mpa, the elongation is greater than 20%, the product of strength and elongation is 25-35 GPa%, the toughness is good, the requirements of the drill rod can be met, the service life is long, the existing drill rod heat treatment tool equipment can be utilized, and the heat treatment process is simple and feasible.
As an alternative embodiment, the steel has the following chemical components in mass fraction: c: 0.05% -0.10%, Si: 0.20% -1.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
As an alternative embodiment, the steel has the following chemical components in mass fraction: c: 0.10% -0.25%, Si: 1.0% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
As an alternative embodiment, the H content of the steel is less than 1.5ppm and the O content of the steel is less than 10ppm in mass fraction
The reason for controlling the H content to be less than 1.5ppm is to control hydrogen embrittlement, and an excessive value of the H content has an adverse effect of easily causing delayed fracture.
The reason for controlling the O content to less than 10ppm is to improve the contact fatigue property, and the adverse effect of excessively large content is to easily form large-grained inclusions to reduce the contact fatigue property.
As an alternative embodiment, the microstructure of the steel is, in volume fraction: the microstructure of the steel is, in volume fraction: 85-94% of lath martensite, 5-10% of retained austenite and 1-5% of carbide.
85-94% of lath martensite has the function of improving the strength of a matrix, the adverse effect that the volume fraction is too high in strength and easy to brittle fracture is caused, and the strength cannot meet the requirement of rock drilling is caused due to too small adverse effect;
5-10% volume fraction of residual austenite is used for reinforcing the product of strength and elongation of steel, the adverse effect of excessively large volume fraction is that the rigidity of a drill rod with excessively high toughness is reduced, and the adverse effect of excessively small volume fraction is that the toughness of the steel is reduced;
the volume fraction of the carbide is determined by the volume fractions of the above two.
As an alternative embodiment, the lath martensite has a width of 0.2-0.6 μm, the equivalent grain size of the retained austenite is 120-460nm, and the carbide size is 20-100 nm.
According to another exemplary embodiment of the invention, a medium manganese drill rod is provided, and the medium manganese drill rod is made of the low-carbon medium manganese steel. In the course of the invention, the application finds that the material of low-carbon medium-manganese steel is particularly suitable for manufacturing taper drill rods.
The process flow of the drill rod is smelting, hot rolling and heat treatment, the welding performance of the drill rod does not need to be considered in the production process, and the drill rod can adapt to the heat treatment specification of medium manganese steel.
According to another exemplary embodiment of the present invention, there is provided a method of manufacturing a medium manganese drill rod, the method including:
s1, obtaining a billet of the low-carbon medium manganese steel;
s2, carrying out center drilling on the steel billet and installing a core material; obtaining square steel of low-carbon medium manganese steel; in the embodiment, the size of the square steel is 150 multiplied by 150mm, and the diameter of the central hole is 48-52 mm;
s3, heating the square steel for the first time, and then carrying out hot rolling, sizing, cooling and core pulling to obtain a drill rod primary product; the first heating temperature is controlled to be 1150-1250 ℃; in the embodiment, the diameter of the primary drill rod product is 20mm-80 mm; the hot rolling temperature is 900-1150 ℃; the sizing temperature is 900-1000 ℃;
s4, carrying out secondary heating, heat preservation and controlled cooling treatment on the primary drill rod to obtain a medium manganese drill rod; the second heating temperature is 800-950 ℃, and the heat preservation time is 2-48 h.
The purpose of the step S2 is to eliminate the structural stress for segregation and other metallurgical defects, refine the prior austenite grain size; the reason for controlling the first heating temperature at 1150-1250 ℃ is to control the proper austenite grain size and element diffusion degree, the adverse effect of over-large temperature is that the austenite grain is over-large, and the adverse effect of over-small temperature is that the alloy element is heavily segregated.
The purpose of the step S3 is to control the formation of lath martensite/retained austenite/carbide complex phase microstructure, the reason that the secondary heating temperature is 800-950 ℃ is to re-austenitize the S2 obtained structure, and the proper austenitizing temperature can obtain the initial good structure.
The reason for the holding time of 2h to 48h is to homogenize the austenite structure sufficiently.
As an alternative embodiment, the method for preparing a steel billet comprises:
s1.1, obtaining raw materials, wherein the raw materials are prepared according to the following mixture ratio: the weight percentage is as follows: c: 0.05% -0.25%, Si: 0.20% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities;
s1.2, smelting the raw materials, refining in an LF furnace, VD vacuum and continuously casting to obtain a billet.
As an alternative embodiment, the controlled cooling process comprises: cooling the primary drill rod product to 10-200 ℃ at the cooling rate of 20-35 ℃, then heating to 600-900 ℃, preserving heat for 10-480 min, and then cooling to room temperature.
The purpose of controlling the cooling rate to be 20-35 ℃ is to ensure that the steel material obtains a complete martensite structure
The purpose of cooling to 10-200 ℃ is to cool the steel below the martensite temperature;
the temperature is raised to 600-900 ℃ for regulating the structure ratio of martensite to residual austenite;
the purpose of the heat preservation for 10min-480min is to make the residual austenite generate transformation and carbide precipitation.
The low-carbon medium-manganese steel and medium-manganese drill rods and the preparation method thereof according to the present application will be described in detail below with reference to examples, comparative examples and experimental data.
Example 1
The low-carbon medium manganese steel comprises the following chemical components in percentage by mass: 0.05% of C, 0.20% of Si, 5.0% of Mn, 0.010% of P, 0.001% of S, and the balance of Fe and inevitable impurities;
smelting in an electric furnace or a converter → refining in an LF furnace → VD vacuum → continuous casting → after drilling in the center, loading a core material to obtain the low-carbon medium manganese steel square steel with the size of 150 multiplied by 150mm and the diameter of the center hole of 48 mm. In the refining process, the mass percent of P in the molten steel is not higher than 0.015, the mass percent of S is not higher than 0.005, and the contents of [ H ] and [ O ] are respectively less than 1.5ppm and 15 ppm; and drilling the center of the continuously cast square billet and then loading a core material. Heating the manganese square steel in the obtained core material to 1150 ℃ for heat preservation, and then performing hot rolling → sizing → slow cooling to room temperature → core pulling to obtain a drill rod; and heating the obtained drill rod to 800 ℃, preserving heat for 2 hours, then cooling to 10 ℃ at a cooling rate of 20 ℃, then heating to 600 ℃, preserving heat for 10 minutes, and then cooling to room temperature to obtain the drill rod containing lath martensite/retained austenite/carbide.
Example 2
The low-carbon medium manganese steel comprises the following chemical components in percentage by mass: 0.10% of C, 1.0% of Si, 9.0% of Mn, 0.010% of P, not more than 0.001% of S, and the balance of Fe and inevitable impurities;
after smelting in an electric furnace or a converter → refining in an LF furnace → VD vacuum → continuous casting → central drilling and then loading a core material, the low-carbon medium manganese steel square steel with the size of 150 multiplied by 150mm and the diameter of a central hole of 52mm is obtained. In the refining process, the mass percent of P in the molten steel is not higher than 0.015, the mass percent of S is not higher than 0.005, and the contents of [ H ] and [ O ] are respectively less than 1.5ppm and 15 ppm; and drilling the center of the continuously cast square billet and then loading a core material. Heating the obtained manganese square steel in the core material to 1250 ℃, preserving heat, and then performing hot rolling → sizing → slow cooling to room temperature → core pulling to obtain a drill rod; and heating the obtained drill rod to 900 ℃, preserving heat for 48 hours, cooling to 200 ℃ at a cooling rate of 35 ℃, then heating to 750 ℃, preserving heat for 480 minutes, and then cooling to room temperature to obtain the drill rod containing lath martensite/retained austenite/carbide.
Example 3
The low-carbon medium manganese steel comprises the following chemical components in percentage by mass: 0.25% of C, 2.0% of Si, 7.0% of Mn, 0.010% of P, 0.001% of S, and the balance of Fe and inevitable impurities;
smelting in an electric furnace or a converter → refining in an LF furnace → VD vacuum → continuous casting → after drilling in the center, loading a core material to obtain the low-carbon medium manganese steel square steel with the size of 150 multiplied by 150mm and the diameter of the center hole of 48-52 mm. In the refining process, the mass percent of P in the molten steel is not higher than 0.015, the mass percent of S is not higher than 0.005, and the contents of [ H ] and [ O ] are respectively less than 1.5ppm and 15 ppm; and drilling the center of the continuously cast square billet and then loading a core material. Heating the obtained manganese square steel in the core-containing material to 1200 ℃, preserving heat, and then performing hot rolling → sizing → slow cooling to room temperature → core pulling to obtain a drill rod; and heating the obtained drill rod to 925 ℃, preserving heat for 25 hours, cooling to 100 ℃ at a cooling rate of 27 ℃, then heating to 820 ℃, preserving heat for 200 minutes, and then cooling to room temperature to obtain the drill rod containing lath martensite/retained austenite/carbide.
Comparative example 1
The low-carbon medium manganese steel comprises the following chemical components in percentage by mass: 0.01% of C, 0.1% of Si, 9.0% of Mn, 0.010% of P, not more than 0.001% of S, and the balance of Fe and inevitable impurities;
after smelting in an electric furnace or a converter → refining in an LF furnace → VD vacuum → continuous casting → central drilling and then loading a core material, the low-carbon medium manganese steel square steel with the size of 150 multiplied by 150mm and the diameter of a central hole of 52mm is obtained. In the refining process, the mass percent of P in the molten steel is not higher than 0.015, the mass percent of S is not higher than 0.005, and the contents of [ H ] and [ O ] are respectively less than 1.5ppm and 15 ppm; and drilling the center of the continuously cast square billet and then loading a core material. Heating the manganese square steel in the obtained core material to 1250 ℃, preserving heat, and then performing hot rolling → sizing → slow cooling to room temperature → core pulling to obtain a drill rod; and heating the obtained drill rod to 900 ℃, preserving heat for 48 hours, cooling to 200 ℃ at a cooling rate of 35 ℃, then heating to 750 ℃, preserving heat for 480 minutes, and then cooling to room temperature to obtain the drill rod containing lath martensite/retained austenite/carbide.
Comparative example 2
The low-carbon medium manganese steel comprises the following chemical components in percentage by mass: 0.30% of C, 2.5% of Si, 9.0% of Mn, 0.010% of P, not more than 0.001% of S, and the balance of Fe and inevitable impurities;
after smelting in an electric furnace or a converter → refining in an LF furnace → VD vacuum → continuous casting → central drilling and then loading a core material, the low-carbon medium manganese steel square steel with the size of 150 multiplied by 150mm and the diameter of a central hole of 52mm is obtained. In the refining process, the mass percent of P in the molten steel is not higher than 0.015, the mass percent of S is not higher than 0.005, and the contents of [ H ] and [ O ] are respectively less than 1.5ppm and 15 ppm; and drilling the center of the continuously cast square billet and then loading a core material. Heating the manganese square steel in the obtained core material to 1250 ℃, preserving heat, and then performing hot rolling → sizing → slow cooling to room temperature → core pulling to obtain a drill rod; and heating the obtained drill rod to 900 ℃, preserving heat for 48 hours, cooling to 200 ℃ at a cooling rate of 35 ℃, then heating to 750 ℃, preserving heat for 480 minutes, and then cooling to room temperature to obtain the drill rod containing lath martensite/retained austenite/carbide.
Comparative example 3
The low-carbon medium manganese steel comprises the following chemical components in percentage by mass: 0.10% of C, 1.0% of Si, 9.0% of Mn, 0.010% of P, not more than 0.001% of S, and the balance of Fe and inevitable impurities;
after smelting in an electric furnace or a converter → refining in an LF furnace → VD vacuum → continuous casting → central drilling and then loading a core material, the low-carbon medium manganese steel square steel with the size of 150 multiplied by 150mm and the diameter of a central hole of 52mm is obtained. In the refining process, the mass percent of P in the molten steel is not higher than 0.015, the mass percent of S is not higher than 0.005, and the contents of [ H ] and [ O ] are respectively less than 1.5ppm and 15 ppm; drilling a hole in the center of the continuously cast square billet, and then loading a core material. Heating the manganese square steel in the obtained core material to 1000 ℃, preserving heat, and then performing hot rolling → sizing → slow cooling to room temperature → core pulling to obtain a drill rod; and heating the obtained drill rod to 700 ℃, preserving heat for 48 hours, then cooling to 300 ℃ at a cooling rate of 5 ℃, then heating to 1000 ℃, preserving heat for 480 minutes, and then cooling to room temperature to obtain the drill rod containing lath martensite/retained austenite/carbide.
Comparative example 4
The low-carbon medium manganese steel comprises the following chemical components in percentage by mass: 0.10% of C, 1.0% of Si, 9.0% of Mn, 0.010% of P, not more than 0.001% of S, and the balance of Fe and inevitable impurities;
after smelting in an electric furnace or a converter → refining in an LF furnace → VD vacuum → continuous casting → central drilling and then loading a core material, the low-carbon medium manganese steel square steel with the size of 150 multiplied by 150mm and the diameter of a central hole of 52mm is obtained. In the refining process, the mass percent of P in the molten steel is not higher than 0.015, the mass percent of S is not higher than 0.005, and the contents of [ H ] and [ O ] are respectively less than 1.5ppm and 15 ppm; and drilling the center of the continuously cast square billet and then loading a core material. Heating the manganese square steel in the obtained core material to 1300 ℃ for heat preservation, and then performing hot rolling → sizing → slow cooling to room temperature → core pulling to obtain a drill rod; and heating the obtained drill rod to 1000 ℃, preserving heat for 48 hours, cooling to 5 ℃ at a cooling rate of 50 ℃, then heating to 500 ℃, preserving heat for 480 minutes, and then cooling to room temperature to obtain the drill rod containing lath martensite/retained austenite/carbide.
Experimental example:
the drill rods obtained in examples 1 to 5 and comparative examples 1 to 6 were subjected to the performance test, and the test results are shown in the following table.
| Tensile strength | Yield strength | Elongation percentage | Product of strength and elongation | |
| Example 1 | 1250 | 900 | 25 | 31 |
| Example 2 | 1300 | 950 | 20 | 26 |
| Example 3 | 1350 | 1000 | 20 | 27 |
| Comparative example 1 | 1000 | 800 | 15 | 15 |
| Comparative example 2 | 1500 | 1300 | 5 | 7.5 |
| Comparative example 3 | 900 | 800 | 10 | 9 |
| Comparative example 4 | 1000 | 900 | 8 | 8 |
From the data in examples 1-3, it can be seen that: the drill rod prepared by the method provided by the embodiment of the application has tensile strength of more than 1250Mpa, yield strength of more than 900Mpa, elongation of more than 20 percent, and product of strength and elongation of 25-35GPa, good toughness, long service life, and can meet the requirements of the drill rod, and the data of comparative examples 1 and 2 and the embodiment show that: the chemical components of the invention can obtain proper product of strength and elongation; from the comparative example 3, comparative example 4 and example data it can be seen that: under the chemical composition of the invention, the proper product of strength and elongation can be obtained by matching with the preparation method.
The drawings illustrate in detail:
FIG. 2 is a scanning electron microscope image of the drill rod microstructure provided in this example 2, from which it can be seen that: the microstructure of the obtained medium manganese steel is a complex phase structure of lath martensite, residual austenite and carbide;
FIG. 3 is a scanning electron microscope image of the microstructure of the drill rod provided in this example 3, and it can be seen that: the microstructure of the obtained medium manganese steel is a complex phase structure of lath martensite, residual austenite and carbide;
one or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
(1) the low-carbon medium manganese steel provided by the embodiment of the invention takes Mn as a main alloy element, does not need to add Ni, Mo and other elements, and has low alloy cost;
(2) compared with the traditional drill rod, the drill rod manufactured by the embodiment of the invention has the advantages that the tensile strength is more than 1250Mpa, the yield strength is more than 900Mpa, the elongation is more than 20%, the product of strength and elongation is 25-35 GPa%, the toughness is good, the requirement of the drill rod can be met, and the service life is long;
(3) the low-carbon medium manganese steel provided by the embodiment of the invention can utilize the existing drill rod heat treatment tool equipment, and the heat treatment process is simple and feasible.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (5)
1. The medium manganese drill rod is characterized by being prepared from low-carbon medium manganese steel, and the steel comprises the following chemical components in percentage by mass:
c: 0.05% -0.25%, Si: 0.20% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities, wherein the microstructure of the steel comprises the following components in percentage by volume: 85-94% of lath martensite, 5-10% of residual austenite and 1-5% of carbide, wherein the width of the lath martensite is 0.2-0.6 mu m, the equivalent grain size of the residual austenite is 120-460nm, the size of the carbide is 20-100nm, the tensile strength of the medium manganese drill rod is more than 1250Mpa, the yield strength is more than 900Mpa, the elongation is more than 20%, and the product of strength and elongation is 25-35 GPa%, and the preparation method of the medium manganese drill rod comprises the following steps:
obtaining a billet of low-carbon medium-manganese steel;
carrying out center drilling and core material loading on the steel billet; obtaining square steel of low-carbon medium manganese steel;
heating the square steel for the first time, and then carrying out hot rolling, sizing, cooling and core pulling to obtain a drill rod primary product; the temperature of the first heating is controlled to be 1150-1250 ℃;
carrying out secondary heating, heat preservation and controlled cooling treatment on the primary drill rod product to obtain a medium manganese drill rod; the temperature of the second heating is 800-950 ℃, and the heat preservation time is 2-48 h;
the controlled cooling treatment comprises the following steps:
cooling the primary drill rod product to 10-200 ℃ at the cooling rate of 20-35 ℃, then heating to 600-900 ℃, preserving heat for 10-480 min, and then cooling to room temperature.
2. A medium manganese drill rod according to claim 1, characterized in that the chemical composition of the steel is, in mass fraction:
c: 0.05% -0.10%, Si: 0.20% -1.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
3. The medium manganese drill rod according to claim 1, characterized in that the chemical composition of the steel is, in mass fraction:
c: 0.10% -0.25%, Si: 1.0% -2.0%, Mn: 5.0% -9.0%, P: less than or equal to 0.010 percent, S: less than or equal to 0.001 percent, and the balance of Fe and inevitable impurities.
4. The medium manganese drill rod according to claim 1, characterized in that the H content of the steel is less than 1.5ppm and the O content of the steel is less than 10ppm, in mass fraction.
5. The medium manganese drill rod of claim 1, wherein the method of preparing the billet comprises:
obtaining raw materials, wherein the raw materials are prepared according to a ratio;
and smelting the raw materials, refining in an LF furnace, performing VD vacuum and continuously casting to obtain the billet.
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